Effect of mechanical ventilation on indoor environment and condensation in high-humidity industrial buildings during winter: field investigation and numerical study

Ventilation is a common method of exhausting humid air from industrial buildings. However, when outdoor temperature is low during winter, cold ventilation airflow not only reduces temperature but also causes severe condensation in high-humidity industrial buildings. This study investigates the effect of mechanical ventilation on the indoor environment of high-humidity industrial buildings during winter by field investigation and numerical simulation. The results show that three stages of indoor thermal and humid environments exist as ACH increases. When ACH=0, the indoor environment lies in the “Warm-Fog Stage”, where water vapor fails to be effectively removed, leading to significant condensation. For low ventilation rate (ACH<5), the cooling effect of cold supply air dominates, causing condensation deterioration. The amount of condensation in the occupied zone is instead 3.3 times that at ACH=0. As ACH increases (5≤ACH≤15), the condensation region reduces as more water vapor is exhausted by ventilation airflow, but the indoor temperature declines to an unacceptable limit, marking the “Cold-Fog Stage”. When the ventilation rate is higher (ACH>15), the cold supply air lifts the condensation region above the occupied zone. However, the indoor temperature is close to the outdoors, resulting in the “Cold-Dry Stage” with poor thermal comfort. In effect, it is difficult to achieve both temperature and condensation requirements in high-humidity plants only through mechanical ventilation. Combined with supply air heating, a lower ventilation rate and higher temperature configuration can provide a relatively energy-efficient strategy.